feat: add gather.is social network tool

[philmade]

Summary

• Adds GatherIs class to useful_tools/ — lets ConnectOnion agents interact with gather.is, a social network for AI agents
• Four methods: browse_feed(), discover_agents(), post(), comment()
• Auth uses Ed25519 challenge-response via PyNaCl (already a dependency)
• Posting solves hashcash proof-of-work (anti-spam)
• Public endpoints (feed, agents) work without auth
• Includes unit tests following test_web_fetch.py patterns

Why

Gather.is is a social layer for AI agents — a shared space where agents post updates, discover each other, and discuss topics. This integration lets ConnectOnion agents participate in that network using the same Agent(tools=[GatherIs()]) pattern as existing tools.

Usage

from connectonion import Agent, GatherIs

gatheris = GatherIs()  # Reads key from GATHERIS_PRIVATE_KEY_PATH or ~/.co/gatheris_private.pem
agent = Agent("researcher", tools=[gatheris])

# Agent can now:
# - browse_feed(limit=25, sort="recent")  → read the public feed
# - discover_agents(limit=20)             → see who's on the platform
# - post(title, summary, body, tags)      → publish (requires auth + PoW)
# - comment(post_id, body)                → comment on posts (requires auth)

Files changed

File	Change
connectonion/useful_tools/gatheris.py	New — GatherIs tool class
connectonion/useful_tools/__init__.py	Export GatherIs
connectonion/__init__.py	Export GatherIs at package level
tests/unit/test_gatheris.py	New — unit tests

Test plan

• Unit tests for all public methods (mocked HTTP)
• Integration test: GatherIs registers tools with Agent
• PoW solver test: verifies solution is cryptographically valid
• Error handling: connection failures, missing auth, empty responses

🤖 Generated with Claude Code

[wu-changxing]

pls use the connection public key and private key pairs to do the auth